Screened hardcopy reproduction apparatus compensation data calculation

Abstract

A method of calculating compensation data for compensating for spatial print engine non-uniformity of an image applied by a print engine to a receiver. A test target has two test areas of different output densities, each with a single output pixel level. A relationship between output density and output pixel level for the print engine is determined, and is used to calculate the output pixel level for each test area from the respective output density. The test target is printed, and the reproduced densities of the test areas are measured at a plurality of different locations in each area. A processor is used to calculate the compensation data using the measured densities. The compensation data defines a relationship between an output pixel location on the receiver, an output pixel level, and a compensated pixel level.

1 . A method of calculating compensation data for compensating for spatial print engine non-uniformity of an image applied by a print engine to a receiver, comprising:
 selecting a test target having at least two test areas of different output densities; wherein each of the at least two test areas has a respective single output pixel level, and includes a plurality of pixel locations;   determining a relationship between output density and output pixel level for the print engine;   calculating the output pixel level for each of the at least two test areas from the respective output density using the determined relationship;   using the print engine to apply the test target to the receiver, wherein the print engine applies to the receiver at each of the plurality of pixel locations in each of the at least two test areas an amount of toner corresponding to the respective output pixel level of the test area and the print engine non-unifomity;   measuring the reproduced densities of the at least two test areas at a plurality of different locations in each of the at least two areas; and   using a processor to calculate the compensation data using the measured densities, wherein the compensation data defines a relationship between an output pixel location on the receiver, an output pixel level, and a compensated pixel level.   
     
     
         2 . The method according to  claim 1 , wherein the print engine is an electrophotographic print engine. 
     
     
         3 . The method according to  claim 1 , wherein the output pixel level has an output-level bit depth, the compensated pixel level has a compensated-level bit depth, and the compensated-level bit depth is greater than the output-level bit depth. 
     
     
         4 . The method according to  claim 1 , wherein the step of selecting the test target further includes selecting the output densities based on selected tonescale characteristics.